1. Field of the Invention
The present invention relates, in general, to battery covers for prevention of electrolyte leakage and, more particularly, to a battery cover for prevention of electrolyte leakage, in which a sealed assembly structure of upper and lower covers of a battery case is configured in such a way that it forms a labyrinth structure that can allow an electrolyte to move upward and downward, thereby increasing an electrolyte leakage resistance of the battery case, and in which gas discharge holes and micro-holes are formed so as to easily discharge gas from the battery case, and in which electrolyte recovery ports are arrayed in such a way that the electrolyte can be prevented from leaking from the battery case even when the battery case is turned over or is tilted to one side.
2. Description of the Related Art
A battery is a device that can supply electricity by discharging charged electricity. A rechargeable battery that can be recycled by repeating electricity charge and discharge processes a predetermined number of times is so called as a secondary battery or as a storage battery (hereinbelow, referred to simply as a battery).
Batteries are classified into a variety of types according to materials of positive and negative plates and a material of an electrolyte, in which a battery using lead as the material of the positive and negative plates and using a sulfuric acid as the electrolyte is named a lead-acid battery.
The lead-acid battery includes polar plates used as positive and negative plates, terminals, a separator that physically and electrically separates the two polar plates from each other, an electrolyte and a battery case that receives the elements therein. Further, a gas discharge port is typically formed in the sealed battery case so as to discharge hydrogen gas generated from the charge and discharge processes and to discharge gas generated from evaporation of the electrolyte.
An example of the lead-acid batteries is a battery that is operated by repeating the discharge and charge processes through a reversible reaction represented by a chemical reaction formula: PbO2+H2SO4PbSO4+2H2O. The battery outputs electricity through discharging and stores input electricity therein through charging.
The lead-acid battery uses a chemical reaction in which the polar plates of lead dioxide (PbO2) and an electrolyte of sulfuric acid (H2SO4) are changed into lead sulfate (PbSO4) and water (H2O). When the lead dioxide and the sulfuric acid are changed into lead sulfate (PbSO4) and water (H2O) in the lead-acid battery, electricity is generated and discharged. On the contrary, when the lead-acid battery is charged, substitution is performed.
Every time the above-mentioned chemical reaction is performed, heat is generated in the battery and causes the electrolyte to partially vaporize and a small quantity of hydrogen gas to be generated, so it is required to discharge the gas from the battery into the atmosphere so as to prevent the battery from exploding.
Further, a vehicle battery is directly affected by the jolting vibration of a vehicle during a movement of the vehicle, so it is required that an electrolyte be prevented from leaking from the battery to the outside through the gas discharge port.
Examples of conventional techniques that were proposed to discharge gas from the interior of the battery to the outside may be referred to in Korean Patent Application No. 10-2000-0072402 (filed on Dec. 1, 2000) entitled “STRUCTURE FOR DISCHARGING EVAPORATING GAS FROM VEHICLE BATTERY” and to Korean Patent Application No. 10-2008-0050115 (field on May 29, 2008) entitled “VENT PLUG FOR Ni-MH BATTERY”.
FIG. 1 is a view illustrating the functional construction of the vent plug that is a prior art device proposed to prevent a leakage of a battery electrolyte and to discharge gas from the battery.
Hereinbelow, the above-mentioned device will be described in detail with reference to the accompanying drawing, FIG. 1. As shown in the drawing, gas generated in the battery is discharged to the outside through a battery cover 110 that is integrally formed in an upper end of a battery case 200.
Here, the battery cover 110 has a cylindrical structure having predetermined diameter and height. The battery case 200 forms cells and receives positive plates 210, negative plates 220, separators 230 and an electrolyte 240 therein.
The battery cover 110 is provided with electrolyte injection ports that communicate with respective chambers which are defined as divided spaces in the battery case 200 by a plurality of partition walls. A valve 130 is inserted into each electrolyte injection port, with a packing 150 placed around the upper end of the electrolyte injection port so as to seal a gap between the electrolyte injection port and the valve 130.
Further, the cylindrical battery cover 110 has threads in an inner circumferential surface thereof, and a plug that includes a vent cap 120 having threads around an outer circumferential surface thereof is tightened to the cylindrical battery cover 110, with a spring 140 placed in the vent cap, so that the plug can seal the electrolyte injection port.
A gas discharge hole is formed through the upper end of the vent cap 120 so that gas can be discharged to the outside through the gas discharge hole.
The above-mentioned conventional technique provides a structure that can discharge gas from the battery to the outside according to elasticity of the spring 140 and is advantageous in that, when gas is generated in the battery to an extent at which the gas pressure exceeds a predetermined level, the gas can be automatically discharged.
However, the conventional technique is problematic in that gas may not be efficiently discharged due to bad quality of the spring 140. Another disadvantage of the conventional technique resides in that it has a complex construction and many parts, which complicates the production process and increases the time required for production, thereby increasing the production cost.
Further, when a conventional battery is turned over or is tilted to one side, the electrolyte may directly leak from the battery. In the above state, the leaking electrolyte may be partially collected in a space between the valve and the vent cap of the plug in the electrolyte injection port and may corrode the spring.
When the spring of the plug that is placed in the electrolyte injection port of the battery is corroded, the elasticity of the spring is reduced, so that the valve may be undesirably opened even under a low gas pressure, and this may cause the electrolyte to freely leak without resistance. Accordingly, it is required to propose a technique which can efficiently discharge gas from the battery while preventing a leakage of electrolyte without increasing the number of parts, thereby maintaining the production cost at a desired level, and which can recover the leaking electrolyte by collecting the leaking electrolyte and feeding the collected electrolyte into the battery.
Further, the conventional techniques are designed so that most of the gas generated in the battery case can be discharged to the outside both through electrolyte recovery ports and through the electrolyte injection port. In the above state, the gas discharge pressure that functions to discharge the gas to the outside may act on the electrolyte stored in the battery case, thereby undesirably causing a large amount of electrolyte to leak through the recovery ports or through the electrolyte injection port at the same time of the discharge of the gas.